The collisions leading to (1.1) conserve total energy and, in the case of translationally invariant systems, total momentum. Note that conservation of total momentum should not be confused with conservation of the total charge current—the latter is not conserved in any of the systems of interest...
Col l isionsndeview of materialecture13leasetakeanevaluationformre-reading: KJF§9.5 1 COLLISIONSJF§95, 107 2Co n se rvatio n of m o m e ntu mecall..